The present invention relates to switches in general and, in particular, to a new and useful pushbutton switch which includes a movably mounted plunger that engages and moves actuators. While the plunger and actuators both include position-restoring springs, the arrangement is such that the combined forces of the springs do not apply directly to the plunger to restore its position.
Pushbutton switches, which are known from U.S. Pat. No. 4,112,277 and Swiss Patent No. 607,858, have a plunger guide housing in which a plunger can be manually moved in an axial direction against the force of a return spring. At least one switch or control element with a switch or control element housing is secured by screws on the plunger guide housing which contains at least one moving contact. If several control elements are provided, these are arranged in series in the direction of motion of the plunger, with which the moving contacts can be brought from one switching position into another switching position. The actuators are designed so that, in the case of several control elements, the actuator of one control element can displace the actuator of the respective following control element.
The control elements are designed substantially according to Swiss Patent No. 547,542. A return spring acts on the actuator which presses the actuator against one end position, which will here be called the "rest position". By pressing the plunger by hand, the plunger can move the actuator from one end position, namely, the rest position, against the force of the return spring into its other end position, namely, the working position.
When the plunger is pressed and the actuator of the control element or the actuators of the control elements are in their working positions, different forces extending in the direction of motion of the plunger act on the plunger. One of the forces acting on the plunger is the force produced by the plunger-return spring proper which acts directly on the plunger. To this force is added the force exerted by the return spring of the control elements or the return springs of the control elements on the plunger over the actuator or actuators. The total force acting on the plunger in the working position in its direction of motion is thus increased by the control elements, and depends on their number. If the actuators are to be held in their working position, the forces exerted by the return springs on the plunger must naturally be compensated by a corresponding counter-force, whose size depends on the number of control elements. This is a disadvantage which is of particular importance when the pushbutton switch, e.g., according to the above-mentioned U.S. Pat. No. 4,112,277, is designed as a locking switch, because the locking element retaining the plunger in the locked position must then absorb the entire restoring force acting on the plunger.
In the switches known from U.S. Pat. No. 4,112,277 and Swiss Patent No. 607 858, the soldered connections are arranged on the sides of the control elements, which is unfavorable for various applications. These switches have further the disadvantage that the changing of a control element requires the unscrewing and screwing of screws which is relatively tiresome and time consuming.
In other known switches, where the control elements are secured by screws on the plunger guide housing, the switches can only be mounted on a switchboard or on the front panel of an apparatus after the control elements have been disassembled. When these switches are installed, additional screws are required, in addition to the preassembled parts containing the plunger guide housing, the plunger, and the control elements, for securing the element, which must be made available and be screwed on. The installation and the final assembly of the switches are thus more complicated, and the expenditure of time and energy increases, which is likewise a considerable disadvantage.